The first collection of products were called the ‘A Series’, with a door depth of 300mm, which is shallow by today’s standards.
The numerals on the products represent how many (approx.) feet wide the door is, as it still does today. The A1 (300mm), A2, A3 and the widest door at the time the A4 (1200mm).
There was no need for walkways as we know them today and chains were used to open and close the rubber flap door.